DATP CAUSES SPECIFIC RELEASE OF CYTOCHROME-C FROM MITOCHONDRIA

The induction of the Mitochondrial Permeability Transition (MPT) has r ecently been associated with the release of apoptogenic cytochrome c, which could come about in a swelling-dependent or swelling-independent manner. We observed that canonical inducers of MPT (Ca2+, t-butyl hyd roperoxide, atractyloside) induce a swelling-dependent release of cyto chrome c, and that osmotic support of mitochondria with PEG-1000 aboli shes mitochondrial swelling, protein release, and cytochrome c release by these inducers. By contrast, it was observed that dATP is a potent inducer that caused release of cytochrome c in a swelling independent manner, i.e. even in the presence of osmotic support by PEG-1000; in addition this release of cytochrome c is inhibitable by cyclosporin A The dATP-dependent and swelling-independent release of cytochrome c fr om mitochondria is not inhibitable by the protease inhibitor z-VAD, su ggesting that it is not mediated by upstream caspases. This is the fir st report to our knowledge that a chemical compound may directly cause release of cytochrome c from mitochondria, and could explain the toxi city of dATP in the context of the genetic immunodeficiency diseases A denosine Deaminase deficiency and Purine Nucleotide Phosphorylase defi ciency. (C) 1998 Academic Press.